Range indicator



v June 17, 1947. L. A. MEACHAM 'lmzmw RANGE INDICATOR Filed on. 5, 1945 s Sheis-Sheet 1 FIG. I

STARTING PULSE GENEPA ?0-9 START-STEP CIRCUIT TIMING-FUSE GENERATOR 2 2 SWEEP CIRCUIT IN l EN TOR L. A. MEACHAM ATTORNEY June 17, 1947, L. A. MEACHAM 2,422,205

RANGE INDICATOR Filed Oct. 5. 1.945 5 Sheets-Sheet 2 FIG. 2

I l 1 l 1 E- 1 I l 1 l DISTANCE YARDS I 8000 IBOIOO 24000 32000 40000 4a0ol0 TIME MICRO-SECONDS 0 4&0 97.6 I404 l95 .2 240.0 2925 lNl/ENT OR BY L. A. MEACHAM A TTORNEY June 17, 1947. A. MEACHAM RANGE INDICATOR w 3 Q3 M a 4 R M 0 m. mT w h m C MN MW A t m E w W M u 5 l I Filed Oct. 5, 1945 not June 17, 1947. A. MEACHAM RANGE INDICATOR Filed Oct. 5, 1943 5 Sheets-Sheet 4 4 5&3 m3: H 353328 n 4 InQ AU 5 u q 1 INVENTOR L. A. MEACHAM BY mm Q.

R v QM.

A 7'TORNE Y June 17, 1947. MEACHAM 2,422,205

RANGE INDICATOR Filed Oct. 5, 1945 5 Sheets-Sheet 5 RAD/0 REC ' ATTORNEY Patented June 17, 1947 STATE RANGE INDICATOR Larned A. Meacham,

tories, Incorporated, New

on of New York Application October 5, 1943, Serial No. 505,024

8 Claims. (Cl. 2501.66)

This invention relates to electric circuit arrangements adapted to be used for electrical range or distance indicating and particularly to apparatus for producing electrical range pulses which are variably delayed with respect to corresponding reference pulses and for indicating the amount of said delay.

In a specific embodiment of the invention herein shown and described for the purpose of illustration, recurrent pulses of energy are radi ated to an object, echo pulses are received from the object, and an indication of the distance from the pulse radiator and receiver to the object is produced. To produce this distance indication, means are provided for generating range pulses which are delayed with respect to corresponding reference pulses by an amount equal to the delay between the radiated pulses and the corresponding echo pulses. There is provided a range indicator indicate the distance to the object directly, a delay of one microsecond between a radiated pulse and its received echo corresponding to a distance of 16 yards, approximately. A range indicating apparatus of this general type is disclosed in my copending application Serial No. 491,791, filed June 22, 1943, but the apparatus described in this application is in some respects an improvement thereover. Portions of the range indicating apparatus shown and described herein may obviously be substituted for corresponding portions of the range indicating apparatus shown and described in said copending application. There is employed a start-stop circuit, similar to the start-stop circuit of said copending application, upon which are impressed pulses in synchronism with the radiated pulses for causing the generation of a square voltage wave. This wave has a negative portion starting with the pulse impressed upon the circuit, which portion has a duration equal to or preferably greater than th maximum delay occurring between the time of radiation of a pulse and the time of reception of an echo of the radiated pulse. This negative portion is followed by a positive portion which occupies a time interval during which the circuit is returned to its stable waiting condition ready to be started again by a succeeding pulse. A timing wave generator comprising an antiresonant circuit is started due to the abrupt decrease in potential at the start of the negative portion of the wave from the start-stop circuit and the timing wave is quickly quenched due to the positive portion of the start-stop wave. Two triode electronic devices having their anodewhich is preferably calibrated to cathode paths in series with the antiresonant circuit are provided for alternately abruptly interrupting and starting the flow of current through the antiresonant circuit in response to the square wave from the start-stop circuit impressed upon the control electrodes of the triodes simultaneously. A feedback path is provided for maintaining the output voltage of the generator at constant amplitude,

A phase shifter is provided for continuously shifting in either direction, the phase of the wave from the timing Wave generator. The phase shifter comprises an improved Wave generating circuit which produces, under control of the timing wave, two voltage waves which are accurately in quadrature and which start coincidentally with each timing wave train. The production of a prolonged starting transient, such as is produced by a simple resistance-capacity phase splitter, is thus avoided. The wave generator employs an electronic device having a high mutual conductance and such an arrangement of related impedance elements in its anode-cathode circuit that, when a varying potential is impressed upon its control electrode, there are produced at the anode and cathode, respectively, potential waves one of which is proportional to the derivative of the other, that at the cathode being an accurate copy of the impressed potential. When the timing wave applied to the control electrode is sinusoidal and has an initial phase such that there is no abrupt change in instantaneous potential, there is preferably employed a path comprising inductance and resistance in shunt with respect to each other between the anode and a source of anode current and a path comprising capacitance shunted by resistance between the cathode and the current source, the first-mentioned resistance being equal to the capacitive reactance and the second-mentioned resistance being equal to the inductive reactance. The phase shifting circuit also comprises a phase shifter condenser, similar to the phase shifting condenser of said copending application. The timing wave from the phase shifting circuit is amplified and the amplified wave supplied to a pulse generator which produces a series of alternately positive and negative sharp pulses which are accurately spaced by a predetermined interval.

An improved pulse selector is provided for generating a pulse which is coincident with a desired one of each group of timing pulses. This pulse selector makes use of a circuit having resistance R and capacitance C of fixed time constant, the charging of the capacitance being initiated in response to the wave front of each negative portion of the square wave from the startstop circuit. There is provided an electronic device having a plurality of electrodes comprising a cathode, a control electrode and an anode, which device is normally non-conducting and which is made conducting coincidently with one of the timing pulses to cause a selected timing pulse to be generated. The exponentially rising potential due to the charging of the condenser is applied to the control electrode. There i applied to the cathode a potential which is varied by means of a potentiometer, and the timing pulses are superposed on one of these potentials. One of the timing pulses will thus bring the con;- trol grid to a sufficiently high potential with respect to the cathode potential to cause anode current to flow and a range pulse to be produced at the anode, the time of selection of a timing pulse to form a range pulse varying in accordance with the setting of the potentiometer which controls the cathode potential. The resistance of the potentiometer is non-uniformly distributed to correct for the non-linearity of the potential rise due to the charging of the condenser and the potentiometer shaft is geared to the shaft of a phase shifting condenser in the phase shifter so that the delay between the radiated pulse and the selected timing pulse may be varied continuously.

The range indicating apparatus has a small minimum delay, say about one microsecond. A fixed delay circuit, the delay of which is equal to or greater than this minimum delay of the range unit is preferably included in the radio receiver so that when the transmitted pulses are directly impressed upon the receiver, the resulting pulses from the receiver may be made coincident with the corresponding range pulses from the range unit when the range indicator is set for zero dis.- tance. The range pulses are impressed upon one plate and the echo pulses are impressed upon the other plate of a pair of deflecting plates of a cathode ray tube, a linear sweep wave being applied to another pair of deflecting plates for defleeting the cathode ray beam perpendicularly with respect to the deflection due to the field set up by the first pair of plates. To determine the range of an object, the delay of the range unit is Varied until the visible indication due to the range pulses on the screen of the cathode ray tube is in alignment with the indication on the screen due to the echo pulses from the radio receiver. The range of the object from which the echoes are received may then be read on the indicator of the range unit.

If desired, the range pulses which are brought into coincidence with the eccho pulses for causing a range indication to be produced may be used together with the echo pulses to control apparatus for automatically controlling the phase shifting condenser and potentiometer of the range indicator to maintain the range pulses and the echo pulses in synchronism. An apparatus of this type is disclosed in a copending application of B. M. Oliver, Serial No. 491,829, filed June 22, 1943.

An object of this invention is, as will be apparent from the above, to provide improved apparatus for accomplishing the over-all function of the system disclosed in my application Serial No. 491,791. Various novel features, however, of the improved system are not limited in their use to systems of this type and may, in fact. find various uses. Several such features have been mentioned. Definitions of various aspects of the invention are appended in the form of claims.

The invention will now be described with reference to the accompanying drawing in which:

Fig. 1 is a block diagram of a ranging system in accordance with the present invention;

Fig. 2 consists of curves to which reference will be made in describing the invention;

Figs. 3, 4 and 5, when Fig. 3 is placed to the left of Fig. 4 and Fig. 5 is placed to the right of Fig. 4, are a schematic view of a range indicator in accordance with the present invention; and

Figs. 6 to 9, inclusive, are diagrams to which reference will be made in describing the invention.

Referring now particularly to Figs. 1 and 2, there is disclosed a range indicating system in which recurring brief pulses of high frequency eleetromagnetic wave energy are produced by a transmitter l0 and radiated from a directional antenna ll toward an object the distance of which is to be determined and in which the wave pulses reflected from the object are received by antenna I2 and detected by a radio receiver 13. An oscillator I4 produces a sinusoidal Wave having a period somewhat longer than the time required for a radio Wave to travel twice the max imum distance to be measured. Starting pulse generator 15 produces pulses as indicated at a, Fig. 2, at regular intervals, one for each cycle of the sine wave from oscillator I4. It is not essential to the operation of the system, however, that these pulses occur at regular intervals. The starting pulses a which are of very brief duration, say one-quarter microsecond, key the radio transmitter [0 to cause the radiation of corresponding pulses b of high frequency radio energy. The starting pulse generator l5 and radio transmitter l0 may be the same as the impulse generator and radio transmitter described in my copending application supra. The starting pulses a are also impressed upon a range indicator IE! to produce output or range pulses '2' which are delayed by a desired amount with respect to the starting pulses a. The range indicator has a small fixed minimum delay, about one microsecond, and a delay circuit having a delay at least equal to this minimum delay is preferably included in the radio receiver I3 so that the pulses 9' from the receiver and the corresponding range pulses i from the range unit may be adjusted to be coincident when the transmitted pulses b are directly impressed upon the radio receiver 13, and when the range indicator is set for zero distance.

The starting pulses a are impressed upon a start-stop circuit H; of the range unit for generating a square voltage wave 0 having an initial negative portion I! starting coincidently with a starting pulse a and a positive portion l8. The intervals during which the negative portions ll of wave 0 occur mark the active periods of the range indicatingapparatus and the intervals during which thepositive portions 18 occur mark the qu s e er s o e a pa atu h in o e ation. These active periods remain fixed while the quiescent periods may vary with frequency variations of source I4 within a limited range.

The voltage wave 0 produced by the startstop circuit is impressed upon a timing wave generator 20 which generates a succession of trains of constant frequency oscillatory waves 1 the phase of which may be s 'ifted continuously through a pluralityof cycles by turning the handle I26 of a phase-shifter H. The phase shifted timing wave, indicated at e of Fig. 2, starts with an abrupt departure from zero to whatever initial instantaneous amplitude corresponds to its phase position. The period of this oscillatory wave, or a phase shift of the wave through a single cycle, corresponds to the time interval required for a radiated wave to travel through a certain distance and for its echo to return through that distance. The distance represented by a single cycle of the oscillatory wave is the velocity of propagation of the radiated pulse divided by twice the frequency of the oscillatory wave. The timing wave e from the output amplifier of the phase shifter 25 is impressed upon a timing pulse generator 22 which produces alternate positive and negative timing pulses f, a pulse being produced at the beginning of each half cycle of the timing wave. The square wave from the startstop circuit and. the timing pulses from the timing pulse generator are impressed upon a pulse selector 23 which selects one of the timing pulses 25 of each group of timing pulses which is delayed by a desired'interval with respect to the corresponding starting pulse a, as shown at i, Fig. 2. As indicated at g in Fig. 2, an exponentially rising potential 35 having the timing pulses superposed thereon is impressed upon a control electrode of an electronic device and a potential 31 which may be varied by means of a potentiometer is impressed upon the cathode of the electronic device to cause the selection of a pulse 26 which causes the control electrode potential to increase sufficiently with respect to the cathode potential to cause the flow of anode current through the electronic device. The shaft 3 of the potentiometer of the pulse selector 23 is connected through the gears 24 to the shaft 29 of a phase shifting condenser of the phase shifter 2| so that the change in cathode potential 31 is equal to the change in peak potential of a superposed timing pulse, such as pulse 25, due to the phase shift of the timing pulses, the resistance of the potentiometer being tapered to correct for the curvature of the exponentially rising potential Only one pulse of each group of timing pulses appears at the output of the pulse selector 23, the pulses of each group which follow a selected pulse being blocked by the output amplifier of the pulse selector.

The echo pulses 7 are impressed upon one of the vertical deflecting plates 3| of a cathode ray tube 30 and the range pulses 2' are impressed upon the other vertical deflecting plate. If desired, of course, a step pulse may be produced under control of the selected pulse i and impressed upon a vertical deflecting plate of the cathode ray tube for producing a range mark on the cathode ray tube screen as disclosed in my copending application, supra. Any suitable linear sweep wave it may be impressed upon the horizontal deflecting plates of the cathode ray tube 30. As shown, the sweep wave generator 35 is controlled by the starting pulses a from starting pulse generator :5 to maintain the sweep wave in synchronism with the starting pulses. Alternatively the pulses i could be utilized for controlling the sweep wave generator and pulses which are delayed by a short fixed period with respect to the pulses i could be used as the range pulses impressed upon a vertical deflecting plate of the cathode ray tube. By rotating shaft 29 of the phase shifter condenser to which the potentiometer of the pulse selector is geared, a range mark produced by range pulses i may be caused to travel across the luminescent screen of the cathode ray tube until it is brought into alignment with an echo mark produced by echo pulses The distance to the object from which the echo pulses are received may then be read directly from a revolution counter or range indicator 32 attached to shaft 29.

The range indicating apparatus is shown in greater detail in Figs. 3A: and 5 when Fig. 3 is placed to the left of Fig. 4 and Fig. 5 is placed to the right of Fig. 4. A suitable starting pulse generator and radio transmitter are shown in my copending application supra and are therefore not being described in detail herein. The startstop circuit I6 is similar to the start-stop circuit described in said copending application but is designed to prevent the false triggering of the circuit by extraneous pulses of smaller amplitude than that of the starting pulses a. The start-stop circuit employs two electronic triodes VLI and V9], triode VH having a cathode M, a control electrode 42, and an anode 43 and triode V91 having a cathode 43, a control electrode 25 and an anode E6. Negative starting pulses a from the starting pulse generator l5 are applied through a 50-micromicrofarad condenser Cl across 0.5-megohm resistor RI which is connected between the control electrode 42 and the grounded cathode M. The anode 53 is directly conductively connected to the control electrode 35 and the anode 46 is connected to the control grid t; through a condenser C4 the capacity of which is 400 micromicrofarads when a maximum range of 22,000 yards is to be measured. For this range the alternating current source M may have any frequency up to about 4,000 cycles. The cathode is is connected to ground through 15,000- ohm resistor R0 shunted by a 500-micromicrofarad condenser 06. Anode potential is supplied to the anode 33 from the positive terminal of 300- volt battery 51 through series resistors R8 (1,000 ohms) and 0.1-megohm resistor R3, the negative battery terminal being grounded. Positive voltage from source 5! is supplied to anode 45 through series resistors R8, R1 (18,000 ohms) and R5 (18,000 ohms) The positive battery terminal is also connected through series resistors R8 and R5 (56,000 ohms) to the cathode M. A 50-micromicrofarad condenser C5 is connected in shunt with respect to resistor R6. A filter condenser C8! of 0.1 microfarad is connected between the negative terminal of resistor R8 and ground. A resistor R86 of 1.8 megohms is connected between the negative terminal of resistor R8 and control grid 52 to maintain the grid positive with respect to cathode 4| during quiescent periods and thus to lower the input impedance and prevent false operation of the circuit due to extraneous pulses during this period. The negative pulse a applied to the control grid 42 causes the interruption of anode current in triode VLI, to make the potential at anode 43 and at control grid 35 more positive. Anode current is thus caused to flow in triode V91. Triode Vl.l continues to be cut oil and V9.l continues to be conducting during the active period due to the discharge current of condenser C l flowing through the anode-cathode path of triode V9.! and resistor El and the resulting negative bias on the control grid 62. At the end of the active period, this discharge current and the resulting grid bias reach a sufiiciently low value to cause the triode VLI to pass anode current and during the following quiescent period the condenser 04 is again charged through resistors R6 and R7 and the control electrode-cathode path of triode VLI. When the triode V9.I becomes conducting, the potential at the common a current of about terminal of resistors R6 andRl become less positive with respect to ground and, when the con duction through triode V9.1 is interrupted the common terminal of resistors R6 and R! become more positive, thus producing the startstop wave 0. I

The start-stop wave cfrom the start-stop circuit is impressed upon theinput circuits of triodes V2.1 and V2.2 of'the timin wave generator 20. The common terminal of resistors R6 and R7 is connected'through:0.0l-microfarad condenser C1 and 0.01-microfarad condenser C9, to

the control electrode of triode V2.2 which is connected through 'l-megohm resistor RI I to the grounded cathode. The common terminal of resistors R6 and R1 is also connected through condenser C1 nected through l-megohm resistor R9 to the cathode. V2.l and V2.2 may be traced iromthe positive 300-volt terminal through resistor R8, 10,000-ohm resistor RH], the anode-cathode path of triode V2.|, the antiresonant circuit comprising 3.66-

millihenry inductor L2 shunted by LOOO-microand 0.01-mic'rofarad condenser C10 to] the control electrode'oftriode V2.l which is con- The anode current paths for triodes and IOO-micromicrofarad variable condenser C16,

to'gro'und. The-anode of triode V2.2 is connected through 100-ohm resistor RIB to the control electrode and a mid-tap of inductor L2 is connected through 47,000- ohm resistor RM to the cathode. Screen grid potential is supplied to the tube through 20,000-ohm resistor RH) and 100-ohm resistor R? with the common terminal of RIB is one-quarter of I this approXimately 50,000-ohm impedance, onemicrofarad condense1-Cl3and the anode-cathode path of triode V2.2 to ground. The anode-cathode path of tube V2.2 is shunted by -micromicrofarad variable condenser Cl 4. I Condenser C82 of 0.1 microfarad is connected between the oathode of triode V2.1 and ground. The inductance L2 and the condenser C13 are enclosed within a.

This shielded antiresonant.

grounded shield -53.

circuit is placed in a suitable oven (not shown) the temperature of which is maintained constant potential at the cathode with being connected through cathode through 0.1-

The tube V3 has a and Hi8 connected to the microfarad condenser CH.

high mutual conductance and the impedance between the cathode of V3 and ground is sumciently high to cause the alternating component of the respect to ground to be an accurate copy of the potential at the control grid with respect to ground. The steady state impedance of the antiresonantcircuitClB, L2, is about 200,000 ohms and is essentially resisground). .Due to the .autotransformer action between the upper'half of coil Lz and the entire coiLthevoltage at the. lower terminal. will be double that at the mid-tap of coil L2. In other words, a voltage equal to the cathode voltage is impressed upon the grid and the net gain of the in order to avoid frequency variations due to tame During each quiescent period 10 milliamperesflows in the anode current circuit of triodes V2.l and V2.2, the voltage drop across each of the anode-cathode paths of these tubes and that across resistor RIO bein about 100 volts. The interruption of the anode current from the 300-volt source due to the negative portion I! of the start-stop wave impressed upon the control grids of triodes V2.l and V2.2 simultaneously starts the oscillatory timing wave d in the circuit. The oscillatory wave is quenched during the early portion of the quiescent period due to the positive portion I 8 perature change.

of the start-stop wave applied to the control 1' grids of triodes V21 and V2.2. The frequency of the timing wave is 81.955 kilocycles which corresponds to a range of 2,000 yards per cycle. When anode current is flowing in the circuit, condenser C62 is charged to about 100 volts and this charge is maintained during the active periods of the range indicator when the triodes V2.1 and V2.2 are non-conducting. Control of the current by the two triodes, acting simultaneously, results in keeping the potential across C82 or'between'the upper end of L2 and ground constant at all times.

In order that succeeding stages of the range unit say behave uniformly throughout the active period, the timing wave is sustained at constant amplitude by means of a positive feedback which is conveniently provided through the cathode follower action of the electronic device V3 of the phase shifter circuit, as will be described below. The anode-cathode circuit of this tube may be traced from the BOO-volt source through 1,006- ohm resistor R24, inductor Ll of 11.64 millihenries in parallel with 6,000-ohm resistor RI 7, the anode-cathode path, 10,000-ohm resistor Rl5-in parallel with 250-micromicrofarad condenserCl 5 feedback path is equal to unity and,

The re- Since the timing wave is 11 cycles have been generateda small departure from unity gain of the feedback path would not cause an appreciable change in amplitude.

The use of tube V3 and its associated circuit to provide feedback for the oscillatory circuit CI3, L2, is a secondary one. The primary purpose of this circuit is to generate two waves of substantially equal amplitude which are accurately in quadrature with respect to each other starting substantially at the first instant of each wave train. A starting transient, lasting through a considerable fraction of a cycle of the timing wave, such as is produced with a simple resistancecapacity phase splitting circuit, is thus avoided.

The method of obtaining the quadrature voltages will be explained with reference to Figs. 6, 7, 8 and 9, each of which shows the cathode, control electrode and anode of electric discharge device V3. The curves in each figure show the alternating component of the cathode potential Ex, which is substantially the same as the grid potential Ed, the current I through the anode-cathode path and the anode potential EP, all potentials being with respect to ground. In Fig. 9 the two components of current I, namely Is and IRK are also shown.

In Fig. 6 a resistance R is connected between the anode and the positive terminal of the anode voltage source (+B), the negative terminal of the anode voltage source being grounded in each case. A capacitance C is connected between the cathode and ground. The time to is the instant at which the current in the circuit of inductance L2 is interrupted to start the generation of the timing wave. The timing wave potential is impressed upon the grid in each case and it is assumed that the electronic tube has a mutual conmid-tap of inductance lcoil L2 condenser C82 to I when this condition exists; no rapid increase or'decrease in amplitude of the timing wave can occur. .sistance of resistor RM may be varied until this unity gain is obtained.

interrupted after about ductance so large that the difierence between the grid potential EG and the cathode potential Ex is negligible. The current in the circuit is dE E; and E IR- RC' That is, EP is proportional to the derivative of EK. In the absence of tube overloading, this relationship is true for both the steady-state timing wave and the discontinuity at time to. If in the steady state,

In order to make the potential wave equal wave, R is made equal amplitude of the anode to the cathode potential to l/wC so that Rc= (I) Then ' E 2 1 cos wt)=-A cos wt EP and Ex are thus equal in amplitude but 90 degrees out of phase with respect to each other. This arrangement of Fig. 6 sufiers from the fact that no unidirectional space current can flow in the circuit because the cathode is connected to ground only through a condenser. This difficulty can be obviated by connecting a high resistance or a high inductance path across the condenser C but such a, modified circuit would cause the introduction of some phase error.

In the arrangement illustrated in Fig. '1, an inductance L is connected between the positive terminal of the unidirectional voltage source +3 and the anode, and a resistance R is connected between the cathode and ground. In this case lz R and dI L F aw a .1

If, as before,

E =A sin at EP: LAw1(%0s wt and if R=wL, EP=A cos wt. As before, E? and EK a in quadrature and E9 is proportional to to the derivative of En. In this embodiment there is the practical difiiculty that the sudden rise of voltage across the inductance shock-excites it in antiresonance with its stray capacitance and this results in objectionable irregularities in the wave shape.

In the arrangement illustrated in Fig. 8 a resistance R is connected between the anode and a positive terminal of the direct voltage source and an inductance L is connected between the oathode and ground. In this case the current 1 I E di-tconstant of integration and E IR= [E dtR (constant) When the cathode wave Ex starts as shown in Fig. 8, the constant in these expressions acquires a positive value equal to the peak value of the alternating component of current. The current starts up from zero as though from a negative peak in its cycle. If the current were to continue as a pure sinusoidal wave, an increased average current would be required. Since there is no change in the steady-state potentials on the tube electrodes to sustain an increased current, the average value of the current wave returns to its original value exponentially with a time constant which may be shown to be equal to L multiplied by the mutual conductance of the tube.

It should be noted that if the timing wave potential at the grid and cathode were to start a quarter cycle earlier or later, that is, with an abrupt rise or fall of potential to maximum or minimum peak amplitude, the arrangement of Fig. 8 would become feasible because the constant of integration would equal zero, and the arrangements of Figs. 6 and 7 would acquire transient difiiculties in that differentiation of the steep wave front would tend to produce tube overload- The arrangements of Figs. 6 and '7 can be combined as shown in Fig. 9 so that the inductance L and resistance RP in shunt with respect to each other are connected between the anode and the positive terminal of the direct voltage source and resistance RK and capacitance C in shunt with respect to each other are connected between the cathode and ground. This is the arrangement which is specifically utilized in the range unit of Figs. 3, 4 and 5. In this case, if the current Ia through RP equals the current Ic through C and if the current Ir. through L equals the current IRK through Rx,

dE (H L dE J= e= and L -R C' If, as before,

E =A sin wt and =R C= then EP=-A cos wt.

In this embodiment resistance Rx provides a direct current path from the cathode to ground and resistance RP critically damps the undesired oscillations which would be generated due to the shock-excitation of the inductance L if the damping were omitted. In the circuit arrangement shown in Fig. 3, the cathode resistance RK is made up effectively of resistors HA5, RI9 and twice the resistance of RM, all in parallel, since each is in an alternating current path between the oathode and ground. Twice the resistance of RM is effectively in the circuit because of the impedance of the tuned circuit L2, C13. The screen grid capacitor Cl? is returned to the cathode in order that the same alternating current may flow through the anode and cathode impedances. The cathode potential of tube V3 is such with respect to the control grid potential that the grid current is zero at all times. By variation of trimmer condenser C15 in the cathode circuit, it is readily possible to adjust the cathode and anode voltages to exact quadrature. The amplitudes of these voltages are then equal if the inductance of LI has the correct value in relation to the plate and cathode resistances.

In some cases it may be desirable to employ a continuous wave rather than an intermittent wave for the control grid potential EG in which case no difliculty will be experienced due to parasitic oscillations or starting transients as discussed above in connection with Fig. 7 and 8. Moreover, it may be desirable in some cases to employ a potential wave Ec. other than a sine wave. When any variable potential is impressed upon the control electrode, there will be produced at the cathode and anode electrodes, respectively, varying potentials one of which is proportional to the derivative of the other, within the obvious limitations imposed by stray capacitances, tube overloading, and the constant of integration in the case of the circuit of Fig. 8.

There are provided two phase inverter triodes VAL! and V4.2 each for impressing upon opposite sector stator plates of a phase shift condenser C25 timing wave potentials which are 180 degrees out of phase with respect to each other. The anode current path for triode V4.1 may be traced from 300-volt source through resistor R24, 10,00G-ohm resistor R23, the anode-cathode path, 1,500-ohm resistor R22 and 10,000-ohm resistor R2! to ground. The control grid of this triode is connected through l-megohm resistor R29 to the common terminal of resistors R2! and R22. The anode current path for triode V2.2 may similarly be traced from the 300-volt source through resistor R22, 10,000-ohm resistor R28, the anodecathode path, 1,500-ohm resistor R21, and 10,000- ohm resistor R25 to ground. One-megohm resistor R25 connects the control grid to the common terminal of resistors R2? and R25. A 0.1- microfarad condenser C83 provides a low impedance path from the negative terminal of resistor R24 to ground. The cathode of tube V3 is connected through 0.01-microfarad condenser Cl 3 to the control grid of of tube V3 is connected through 0.01-microfarad condenser CI!) to the control grid Of triode V4.2.

The mutual conductance of each of the triodes V41 and V4.2 is suificiently large to cause the cathode potential of each to be an accurate copy of the potential of the corresponding control electrode. As the same current passes through R23 and RZI, by way of the anode-cathode path of V41, the anode potential of VGA is equal in amplitude to the potential at the junction of R2! and R22, but 180 degrees out of phase therewith. Similarly, the anode potential of V4.2 is equal in amplitude to, but 180 degrees out of phase With, the potential at the junction of R25 and R21. In view of the phase relationship established in the circuit of V3, it may be seen that the four lastmentioned potentials are alike in amplitude, but that three of them differ in phase from the fourth by 90 degrees, 180 degrees and 270 degrees, respectively, this relationship being established at essentially the first instant f each timing wave train.

The phase shifter condenser C25 comprises a metallic ring 85, four metallic stator sectors BI, 82, 83 and 8d and a dielectric rotor 87 of a material having a dielectric constant considerably different from that of air. The phase shifter condenser is described in detail in my copending application, supra. The stator sector 84 is connected to the common terminal of resistor R2? and the anode of tube 4.5; stator sector 83 is connected to the common terminal of resistors R2i and R22; stator sector 82 is connected to the common terminal of resistor R23 and the anode of tube 4.2, and stator sector 84 is coniected to the common terminal of resistors R25 ind R21. Condensers C23 and 026 each of nicromicrofarads are connected between stator ectors 8! and 82, respectively, and ground. Varitble 25-microniicrofarad condensers CH and C22 triode VGA and the anode are connected between stator sectors 83 and 84, respectively, and ground, these condensers being variable to allow for accurate balancing of the cathode and anode reactances.

The ring stator 86 of the phase shifter is connected by lead 39 to the input of a two-stage amplifier comprising electronic tubes V5 and V6 and the output of the amplifier is connected to a timing pulse generator circuit comprising electronic tubes VT and V8. The lead 49 is connected through IOU-ohm resistor R33 to the control grid of the tube V5. Anode potential is sup plied to the tube from 300-volt source 5! through LOGO-ohm resistor R36 and 10,000-ohm resistor R25, the anode-cathode path, 180-ohm resistor R32 and LOGO-ohm resistor RM to ground. Control grid biasin potential is provided due to anode current flowing through resistor R32, which bias is applied to the grid through 0.l megohm resistor R29 and 0.47-megohm resistor R30 in series. A 0.01-microfarad condenser C27 connected from the common terminal of resistors R29 and R33] to the cathode of tube V5 by-passes alternating components of the voltage across R32. Screen grid voltage is supplied to tube V5 through resistor R36, 68,000-ohm resistor R3! and ohm resistor R34, the common terminal of resistors R37 and R34 being connected through 0.0l-microfarad condenser C29 to the cathode. Condenser C26 of 0.1 microfarad is connected between ground and one terminal of resistor R36 to suppress voltage variations of the 300-v01t source. The anode of V5 is connected through 0.01-microfarad condenser C28 and 100-ohm resistor R46 to the control rid of amplifier tube V5. Anode voltage is supplied to tube V5 from the 300-volt source through resistor R36, 10,000- ohm resistor R43, the anode-cathode path and -ohm resistor R4! to ground. A 0.1-megohm resistor R38 is connected from the common terminal of condenser C28 and resistor R40 to ground. Screen grid voltage is supplied from the SOD-volt source through resistor R36, 68,000-ohm resistor RM and lOO-ohm resistor R42, the common terminal of resistors R44 and R42 being connected through 0.0l-microfarad condenser C3! to the cathode. Negative feedback is provided by connecting the anode of tube V6 through 0.1- megohm resistor R39 to the cathode of tube V5.

The amplified timing wave voltage at the anode of tube V6 is impressed through 0.0l-microfarad condenser C535 and IOO-ohm resistor R46 upon the control grid of the center clipper tube V! of the timing pulse generator 22. The common terminal of resistor R 56 and condenser C30 is connected through 0.l -megohm resistor R45 to ground and the tube cathode is connected through 1.0,090-ohm resistor R4! shunted by 50-micromierofarad condenser C33 to ground. Anode voltage is supp-lied to tube V! from the 300-volt source through 1,900-0hm resistor R53 and labile-ohm resistor R49, and screen grid voltage applied through IOU-ohm resistor R59 from the voltage divider formed by 33,000-ohm resistor R5! and 33,000-ohm resistor R52, the common terminal of resistors R5! and R52 being connected through 1microfarad condenser C34 to the oathode. Tube V7 acts as a cathode follower during positive half cycles of the timing wave impressed upon its grid and is cut off during the negative half cycles. During the positive half cycles on the grid, when the grid potential first 7 increases and then decreases, the anode potential first decreases and then increases. tube is cut off the anode potential is While the constant.

The anode of tube V1 is connected through 150- micromicrofarad condenser C35 and 100-ohm resistor R56 to the control grid of tube V8, the cathode of which is grounded. Anode voltage is supplied to tube V8 through resistor R53 and 1,500-ohm resistor R51. Screen grid voltage is supplied from the 300-volt source through resistor R53, 0.1-megohm resistor R59 and 100-ohm resistor R58, the common terminal of resistors R59 and R58 being connected through 0.1-microfarad condenser C322 to ground. Condenser C32! of 0.1-microiarad is connected between the negative terminal of resistor R53 and ground. The cathode of tube V1 is made positive with respect to ground due to the connection of the cathode to the common terminal of the voltage dividing resistors Rd: and R48 (1.8 megohms). The grid of tube V8 is biased positively due to its connection to the common terminal of the voltage dividing resistors R54 and R55 (1 megohm) During the quiescent periods when no wave is being generated by the timing wave generator, grid current flows in tube V8 and the grid is at a slightly positive potential. During the active periods when the timing wave is being generated, the change in anode potential of tube V1 causes the grid potential of tube V8 to be sharply decreased at the beginning of one-half cycle of the timing wave and to be sharply increased at the beginning of the following half cycle so that conduction in tube V8 is cut oil and restored alternately. The resulting square wave at the anode of tube V8 is differentiated by means of IOO-micromicrofarad condense-r C36 and 1,500-hm resistor R51, which elements are connected in series between the anode of tube V8 and ground, to produce alternately positive and negative sharp pulses across resistor R61.

The pulse selector 23 comprises a triode electronic device V1.2 and a pentode electronic device Vlil. Anode current is supplied to tube V4.2 from the 300-volt source through LOGO-ohm resistor R13 and l-megohm resistor R62, the cathode being grounded. The common terminal of resistors R13 and R02 is connected through l-megohm resistor R00 to the control electrode. There is provided a condenser charging circuit having a time constant of about 800-microseconds which may be traced from the positive terminal of the 300-volt source through resistors R13, R62. 750-micromicrofarad condenser C38, shunted by lOO-micromicrofarad variable condenser (339, and 1,500-ohm resistor RSI to ground. The common terminal of resistor R62 and condenser C38 is connected through IOU-ohm resistor R63 to the control electrode of tube VII]. The anode current path for this tube comprises resistor R13, 1.8-megohm resistor R64, the anodecathode path, a variable portion of the resistance of 20,000-ohm potentiometer R51 and 680-ohm resistor 81 to ground, the cathode also being connected through 0.003-microfarad condenser GM! to ground. The cathode potential may be varied by moving the variable tap of potentiometer R61, this potentiometer being in a series circuit which may be traced from the BOO-volt source through resistor R13, 40,000-ohm resistor R58 potentiometer R01 and resistor R81 to ground. Screen grid potential is supplied from the common terminal of voltage dividing resistors R (41,000 ohms) and R59 (0.1 megohm) through lOO-ohm resistor R55. Resistor R09 is shunted by 100-micromicroi'arad condenser C42. The square wave 0 from start-stop generator I6 is impressed upon V1.2 through lead 60.

the control grid of tube During the quiescent periods when the startstop wave is positive, the grid of tube V1.2 is positive, grid current being drawn through resistor R60. As a result the anode-cathode resistance of the tube is low and the anode potential is reduced nearly to ground potential (about +1.1 volts). When tube V|.2 is cut off due to the negative portions l1 of start-stop wave 6, condenser C38 and its trimmer C39 are charged through resistor R62 to a potential which rises exponentially toward a 300-volt asymptote. The alternately positive and negative timing pulses which appear across the resistor R6! are applied in series with the exponentially rising condenser voltage to the control grid of tube V10.

The selection of one of the timing pulses of each group of pulses is controlled by varying the setting of potentiometer R61 to vary the cathode potential of tube V10. The first pulse (26) of each group of pulses which raises the grid potential of tube V10 sufficiently with respect to the cathode potential to cause anode current to flow may be designated as the selected pulse since it causes the potential at the anode of tube V10 to drop sharply to control the production of a corresponding range pulse. If the setting of potentiometer R61 were varied progressively without varying the setting of the phase shifter condenser C25, the interval between the radiated pulses b and the corresponding selected pulses or range pulses 26 would vary in steps, the interval of each step corresponding to approximately 12.2 microseconds or a range of 2,000 yards. By coupling potentiometer shaft 34 to the shaft 29 of the phase shifter condenser by means of gears 24, the interval between the radiated pulses and the corresponding selected pulses or range pulses may be varied continuously. The resistance winding of the potentiometer R61 is preferably non-uniformly distributed to correct for the curvature of the exponentially rising voltage across the condensers C38 and C39 so that a change in cathode potential corresponding to a single revolution of the potentiometer shaft 29 will be equal to the potential difference at the grid of tube Vii! between the peak potential of a timing pulse which is to be selected and the peak potential of a succeeding positive timing pulse at any time during each active interval. Instead of superposing the timing pulses upon the exponentially rising control grid potential of tube V10, they may be superposed upon the cathode potential of tube V10 by connecting one plate of each of condensers C38 and C39 directly to ground, connecting the lead from condenser C36 to the cathode of tube VIII and connecting a resistor between the cathode of tube V10 and condenser C40. In this case one of the negative timing pulses is selected.

There is provided an output amplifier comprising electronic devices V9.2 and VH which repeats the selected pulses or range pulses and which suppresses the timing pulses following each of the selected pulses. The anode of tube Vlil is connected through .00O5-microfarad condenser C41 and 1.8-rnegolun resistor R11 in series to ground and the control grid of tube V9.2 is connected to the common terminal of condenser C41 and resistor R11. The anode current path of this tube may be traced from the positive terminal of the 300-v0lt source through resistor R13, 22,000-ohm resistor R12, the anode-cathode path and i'w-ohm biasing resistor 32 to ground, the resistor R82 being shunted by 0.0l-microiarad condenser C69. Filter condenser C323 of 0.1 microfarad is connected between the common ter- 15 minal of resistors R73 and H52 and ground. The anode of tube 9.2 is connected through 100-micromicrofarad condenser CM and 0.1-megohm resistor R2! in series to ground and the common terminal of the condenser and resistor is connected through 100-ohm resistor R1? to the control grid of tube V l 1. Positive biasing potential is provided for the cathode of tube VH by connecting it to the common terminal of the potential dividing resistors R76 (0.22 megohm) and R15 (15,000 ohms) which are connected in series between the negative terminal of resistor R13 and ground, the resistor R75 being shunted by 0.01-- microfarad condenser C46. Anode potential is supplied to tube VH from the 300-volt source through resistor Hi3 and 33,000-ohm resistor R78. Screen grid voltage is also supplied from the 300-volt source through resistor R73, 18,000- ohm resistor R35 and MiG-ohm resistor R19, the common terminal of resistors R79 and R80 being connected through 0.0005-microfarad condenser Ct! to ground. Ihe anode of tube VH is connected through 0.0e2-microfarad condenser C48 and 1,800-ohm resistor R8! in series to ground. The primary winding of output transformer TI is connected across resistor RBI to cause the production of range pulses 1 across the secondary Winding one terminal of which is grounded.

When tube V10 becomes conducting due to a positive timing pulse which is superposed upon the exponentially rising grid potential, the potential at the anode of tube V50 is reduced and condenser C45 discharges through a circuit comprising the anode-cathode path of tube V10 and resistor R 55. Tube V9.2 which normally conducts is thus cut oil? and remains cut off due to the voltage drop across resistor RH during the remainder of the active period and the timing pulses which follow the selected pulse are thus not repeated. The interruption of conduction through tube 512 due to the selected timing pulse causes the production of a positive pulse at the control grid of tube VH, causing it to pass eX- tremely large anode current momentarily, thus producing a negative pulse at the anode of tube V i i. The resulting range pulse at the secondary of transformer Ti may obviously be of either positive or negative polarity as desired. If desired, moreover, this output pulse may be utilized to generate a step as disclosed in my application, supra. A negative pulse is also produced at the common terminal of resistors R89 and R79 to cause EG-micromicrofarad condenser C45 to discharge through a path including the screen grid-cathode path of tube Vii and resistor R?! to reinforce the negative potential at the grid of tube V9.2 so that tube V8.2 is cut ofi very sharply and remains so until the end of the active period.

While triodes VM and VI.2 are shown as individual tubes, these triodes may be within a single evacuated envelope since the triodes are synchronism. Triodes V9.1 and vaz may also be within a single evaciated envelope. Triode VLZ is not placed Withn the same envelope with vhile triode V9.2 is conducting.

The cathode ray device 30 comprises, in addiion to the vertical and horizontal deflecting lates, a cathode H9, anodes E20 and a phos- -horescent screen E23. The sweep wave h prouced by the sweep circuit 35 and applied to the 33 causes the cathode ray beam repeatedly in a horieflecting plates J sweep across the screen zontal direction, for example; The range pulses 26 from the output transformer TI of the range unit are applied to one of the vertical deflecting plates 3| of the cathode ray tube to cause the production of a vertical deflection in one direction upon the screen 123 and the echo pulses 7' from the radio receiver I 3 are applied to the other Vertical deflecting plates 3! to produce a vertical deflection of the cathode ray beam in the opposite direction. By rotating the shaft 29 of the phase shifting condenser C25 of the phase shifter and the shaft 34 of the potentiometer R6! of the pulse selector by means of a handle I26, the visual indication produced by the range pulses 26 may be caused to travel across the screen 123 and brought into alignment with the visual indication produced upon the screen by the echo pulses 7'. The distance to the object from which the echo pulses are received may then be read directly upon the revolution counter or distance indicator 32 which is calibrated in units of distance, each complete revolution of the shaft 29 changing the delay of the range pulses 26 With respect to the corresponding transmitted pulses b by an interval corresponding to 2,000 yards.

In some cases it may be desirable to produce pulses which are delayed with respect to corresponding starting pulses a by impressing only the start-stop wave 0 upon the pulse producing circuit comprising electronic devices V|.2 and VH1, the amount of delay being controlled by the setting of potentiometer R61 and the time constant of the condenser charging circuit comprising resistors RSI and R62 and condensers C38 and C39.

Application Serial No. 573,194, filed January 1'7, 1945, which is a division of the present applicadisclosed herein for What is claimed is:

' an electronic device having an anode, a cathode voltage to cause a desired one of timing pulses to be repeated, and means for indicating the distance of the object when the repeated pulses are coincident with the echo pulses.

l7 trode-cathode circuit a unidirectional voltage which may be varied, means for impressing said timing pulses upon said control electrode-cathode circuit, means for varying said unidirectional each series of 3. Apparatus for repeating one of a group of sequentially produced electric pulses which is delayed by a desired amount with respect to the first pulse of said series comprising an electronic device having a plurality of electrodes comprising a cathode, an anode and a control electrode,

. an anode-cathode circuit including a source of anode current, a current path connecting said control electrode and said cathode, means for generating and impressing upon said current path an exponentially substantially coincidently with the first of said I group of pulses for causing the potential of one I of said control and cathode electrodes to change changing voltage starting exponentially and thereby reduce the potential difference between said electrodes, means for impressing said series of pulses upon said current path, and means for varying independently of said exponentially changing voltage the potential difierence between said control and cathode electrodes for producing a change in anode current coincidently with a desired one of said series of pulses.

4. Apparatus for repeating one of a group of periodically recurring electric pulses which is delayed by a desired amount with respect to the first of said group of pulses comprising an electronic device having a plurality of electrodes comprising a cathode, an anode and a control electrode, an anode-cathode circuit including a source of anode current, a current path connecting said control electrode and said cathode, means for applying to said current path a biasing voltage for normally preventing the flow of anode current in said anode-cathode circuit, means for generating and impressing upon said current path an exponentially changing voltage to reduce the potential difference between said control and cathode electrodes, means for impressing said group of electric pulses upon said current path, and means for varying said biasing voltage for initiating current flow in said anode-cathode circuit in response to a desired one of said electric pulses.

5. Apparatus in accordance with claim 4 in which are provided means for producing in an output circuit a pulse in response to the initiation of current in said anode-cathode circuit and for preventing the production of subsequent pulses in said output circuit while said current continues without interruption in said anode-cathode circuit.

6. Apparatus for producing output pulses which are delayed by a desired time interval with, respect to corresponding reference pulses which comprises means for producing groups of periodically recurring timing pulses which groups are initiated in synchronism with said reference pulses, means for shifting the phase of said timing pulses with respect to corresponding reference pulses, an electronic device having a plurality of electrodes comprising a cathode, an anode and a control electrode, an anode-cathode circuit including a source of anode current, a current path connecting said control electrode and said cathode, means for applying to said current path a biasing voltage for normally preventing current in said anode-cathode circuit, means for varying said biasing voltage, means for generating and impressing upon said current path a voltage which changes in a certain direction with respect to time during the period of each group of saidtiming pulses to increase the potential of said control electrode with respect to that of said cathode, means for impressing said timing pulses upon said current path, means for producing an output pulse in response to the initiation of anode current in said anode-cathode circuit and substantially coincidently therewith, the flow of current in said anode-cathode circuit being initiated in response to one of said timing pulses When the potential of said control electrode has been increased sui ficiently with respect to the potential of said cathode, and means for controlling said biasing voltage varying means and said phase shifting means simultaneously to progressively vary the time interval between said output pulses and the corresponding reference pulses.

7. Means for repeating a desired one of a series of sequentially produced electric pulses which comprises a plurality having an anode, a cathode and a control electrode, an anode current circuit for each or said devices, means for impressing between the control electrode and cathode of a first of said electronic devices a voltage having as components a biasing voltage for normally preventing the flow of anode current in said device, a voltage which changes with respect to time in a direction to make the control grid relatively more positive with respect to the cathode and said series of electric pulses, means for varying said biasing voltage to initiate current in the anode current circuit of said first device coincidently with a desired one of said pulses, means responsive to the anode current in said first device for interrupting the fiow of current in the anode current circuit of a second electronic device and for maintaining the interruption of said current while current is flowing without interruption in the anode current circuit of said first device, and means responsive to the interruption of the anode current in said second device for causing a momentary change of the anode current in a third electronic device thereby generating said repeated pulse.

8. Pulse generating apparatus comprising a space current device having an anode, a cathode and a control electrode, means for supplying space current to said device when said evi is in a conducting condition, a circuit connecting said control electrode and said cathode, means for repeatedly producing and impressing upon said control electrode with respect to a point of reference potential in said circuit an exponentially rising potential, means for impressing a potential upon said cathode with respect to sa1d reference potential, conduction being initiated in said device when the potential of said control electrode has increased suificiently with respect to the potential of said cathode, means for producing a pulse at the time that cdnduction lS initiated in said device and means for vary n the time interval elapsing between the starting time of said exponentially the time of production of said pulse compris ng means for varying said cathode potential with respect to said reference potential.

' LARNED A. MEACHAM.

(References on following page) the flow of anode of electronic devices each 4 rising potential and Number REFERENCES CITED 2103090 The following references are of record in the 2,341,232 file of this patent: 1,924,174 5 2,288,554 UNITED STATES PATENTS 2,364,998 Number Name Date 2,235,131 Wheeler Mar. 18, 1941 2,255,403 Wheeler Sept. 9, 1941 Number 2,277,000 Bingley Mar. 17, 1942' 10 487,982

Name 7 Date Plebanski Dec..,21, .1937 Norton Feb. 8, 1944 Wolf -Aug. 29, 1933 Smith, Jr. June 30, .1942 Palmer et a1. Dec. 12, 1944 FOREIGN PATENTS Country Date Great Britain June.29, 1 938 Disclaimer mmit, N. J. RANGE INDICATOR. Patent dated 2,422,205.-Larned A. Meacham, Su

June 17 1947. Disclaimer filed Sept. 16, 1949, by the assignee, Bell Telephone Laboratories, Incorporated. Hereby enters this disclaimer to [Ofiicial Gazette October 25, 1949.]

claim 8 in said Letters Patent.

Disclaimer 2,422,205.Larned A. Meacham, Summit, N. J. RANGE INDICATOR. Patent dated June 17, 1947. Disclaimer filed Sept. 16, 1949, by the assignee, Bell Telephone Laboratories, Incorporated. Hereby enters this disclaimer to claim 8 [Oflicial Gazette October 25, 1.949.]

in said Letters Patent. 

